The present invention relates to integrated circuit (IC) packaging, and more particularly, to heat spreaders for ball grid array (BGA) and similar IC packages.
In order to assemble or package an integrated circuit device, an IC die is attached to, and electrical conductors connect the die to, a lead frame or a substrate. The assembly is then partially encapsulated in molding compound to make the packaged IC device that is ready for mounting on a circuit board. The packaging serves several functions including protecting the IC die against potentially harmful external forces and substances. Since a die generates heat during operation and since excess heat can damage the die and other device components, the packaging should also be able to dissipate heat from the die to the exterior of the device. Heat spreaders, which are relatively highly thermo-conductive structures—conventionally made of metal, such as, for example, copper—may be used to assist in the dissipation of heat from a die.
In a typical ball grid array (BGA) device, the die is attached to one side of a planar laminate substrate and encapsulated in molding compound. On the other side of the substrate, there is a grid of connection pads to which are attached solder balls for mounting the packaged device on a circuit board. Several conventional ways of incorporating a heat spreader into a BGA packaged device are known.
For example, U.S. Pat. No. 6,432,742 to Guan et al. (“Guan”) teaches assembling a BGA device with a thin heat spreader embedded in the molding compound. The particular heat spreader used in Guan and its attachment to other packaged device components results in tight dimensional tolerance requirements for packaged device elements, which may increase production costs.
In another example, U.S. Pat. No. 7,126,218 to Darveaux et al. (“Darveaux”) teaches using a heat spreader attached directly to the surface of the die in a BGA package. The heat spreader of Darveaux conforms generally to the topological profile of the die, underlying substrate, and bond wires interconnecting the die and the substrate. The molding compound encapsulant completely covers the heat spreader and die, which may reduce thermal conduction efficiency since conventional molding compound is significantly less thermo-conductive than metal.